Multi-generation insects like the vine mealybug are tough to control because all growth stages can be found at the same time in a vineyard.
Fortunately, there are products — many of them long-time broad spectrum pesticides — still available to control these insects.
Yet, there is concern that these products may be short-lived with continued regulatory scrutiny of organophosphates and carbamates.
One of those is Lorsban, which has been an important product for control of vine mealybug, one of the most voracious pests to inflict damage in California grapes.
Lorsban has been used under a Section 18 emergency registration for the past eight years for not only mealybug control, but to control ants, which are a protector of vine mealybug. However, researchers and growers are trying to get away from that with some unique vine mealybug control strategies.
“Vine mealybugs are very prolific,” says Kris O'Connor, president of the Central Coast Vineyard Team (CCVT) in Paso Robles, Calif. “They have the potential to cause quite a bit of economic damage and they're transported easily.
“The good news is we know more about the biology now and their interaction with ants. There has been a lot of hard work and investment by the University of California (UC) on this problem. As a result, we have a lot more options and choices of softer materials now.”
“Vine mealybug is a constant battle,” says Erin Amaral, pest control adviser (PCA) with Pacific Vineyard Co. in San Luis Obispo, Calif. “In some shape or form, we're either monitoring it or treating it. This time of year (mid-summer), we've got all generations — eggs, nymphs and adults. That makes it even more difficult. There are a lot of decisions to be made on how you're going to approach the problem and figure out the best timing for a treatment. Timing is everything with the softer pesticides we're using now.”
Ant control is the key to making a softer approach work, according to Kent Daane, UC Cooperative Extension entomologist/insect biologist at the Kearney Agricultural Center in Parlier, Calif. “Ants disrupt bio-control,” Daane says. “If you want to improve bio-control you have to kill the ants.”
Lorsban was necessary to kill the ants. However, baits that attract and kill ants are now commercially available.
“We've pretty much avoided Category 1 pesticides for the past couple of years,” she says. “We've been working with UC Berkeley on ant baits, as well as doing a lot of research with parasitoids. We actually started with the parasitoids, and then realized ants were the key. Once we found out how to control the ants, we came back with the parasitoids”
This will be the third year Amaral has released parasitoids. Currently they are reared through UC Berkeley's mealybug research program. Next year, they will be available commercially.
Timing from setting out ant baits to releasing parasitoids to applying softer chemistries is critical.
“The best time to put out ant baits is early spring right after the heavy rains quit,” Amaral says. “If you put them out too late, they won't work. Then we start releasing parasitoids in late spring/early summer and release once a week up until harvest.”
When pesticide applications are needed, Amaral uses a variety of products. She uses Applaud for foliar applications and Admire Pro and Venom through the drip system. Again, timing is critical.
“With these newer pesticides you have to hit them in the juvenile stage,” she says. The first and second instar is the ideal time. By the third instar you're starting to push it. Some of these insecticides are growth regulators, so if they're adults, you're not going to kill them.”
Other options are also promising. “We are all waiting for Movento,” Daane recently told attendees at UC's Central Coast Research Road Show in Paso Robles, Calif. That wait is now over as Movento (spirotetramat), a new foliar product from Bayer CropScience, was registered by the California Department of Pesticide Regulation (CDPR) on July 14. The product moves both through the xylem as well as the phloem, which should offer expanded control of mealybug when the pest is under the bark.
“I do want to use it, but I'm waiting until the European maximum tolerance levels are set,” Amaral says. “I've seen it work out here on a very small research trial. I've heard that it does take some time and patience, but we're all about patience here.”
Through extensive research by UC, groups such as the CCVT and individual cooperators, there has been tremendous progress made in a few short years in managing vine mealybug. “There are some growers who have completely eliminated organophosphates and carbamates from their program,” O'Connor says. “If you can handle the ant problem, biological controls and reduced risk materials can work. However, if you don't control the ants, that approach won't work at all. You really have to be looking at the overall mealybug/ant complex.”